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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef nsCategoryCache_h_
#define nsCategoryCache_h_
#include "mozilla/Attributes.h"
#include "nsIObserver.h"
#include "nsServiceManagerUtils.h"
#include "nsCOMArray.h"
#include "nsInterfaceHashtable.h"
#include "nsXPCOM.h"
#include "MainThreadUtils.h"
class nsCategoryObserver final : public nsIObserver {
~nsCategoryObserver();
public:
explicit nsCategoryObserver(const nsACString& aCategory);
void ListenerDied();
void SetListener(void(aCallback)(void*), void* aClosure);
nsInterfaceHashtable<nsCStringHashKey, nsISupports>& GetHash() {
return mHash;
}
NS_DECL_ISUPPORTS
NS_DECL_NSIOBSERVER
private:
void RemoveObservers();
nsInterfaceHashtable<nsCStringHashKey, nsISupports> mHash;
nsCString mCategory;
void (*mCallback)(void*);
void* mClosure;
bool mObserversRemoved;
};
/**
* This is a helper class that caches services that are registered in a certain
* category. The intended usage is that a service stores a variable of type
* nsCategoryCache<nsIFoo> in a member variable, where nsIFoo is the interface
* that these services should implement. The constructor of this class should
* then get the name of the category.
*/
template <class T>
class nsCategoryCache final {
public:
explicit nsCategoryCache(const char* aCategory) : mCategoryName(aCategory) {
MOZ_ASSERT(NS_IsMainThread());
}
~nsCategoryCache() {
MOZ_ASSERT(NS_IsMainThread());
if (mObserver) {
mObserver->ListenerDied();
}
}
void GetEntries(nsCOMArray<T>& aResult) {
MOZ_ASSERT(NS_IsMainThread());
LazyInit();
AddEntries(aResult);
}
/**
* This function returns an nsCOMArray of interface pointers to the cached
* category enries for the requested category. This was added in order to be
* used in call sites where the overhead of excessive allocations can be
* unacceptable. See bug 1360971 for an example.
*/
const nsCOMArray<T>& GetCachedEntries() {
MOZ_ASSERT(NS_IsMainThread());
LazyInit();
if (mCachedEntries.IsEmpty()) {
AddEntries(mCachedEntries);
}
return mCachedEntries;
}
private:
void LazyInit() {
// Lazy initialization, so that services in this category can't
// cause reentrant getService (bug 386376)
if (!mObserver) {
mObserver = new nsCategoryObserver(mCategoryName);
mObserver->SetListener(nsCategoryCache<T>::OnCategoryChanged, this);
}
}
void AddEntries(nsCOMArray<T>& aResult) {
for (auto iter = mObserver->GetHash().Iter(); !iter.Done(); iter.Next()) {
nsISupports* entry = iter.UserData();
nsCOMPtr<T> service = do_QueryInterface(entry);
if (service) {
aResult.AppendElement(service.forget());
}
}
}
static void OnCategoryChanged(void* aClosure) {
MOZ_ASSERT(NS_IsMainThread());
auto self = static_cast<nsCategoryCache<T>*>(aClosure);
self->mCachedEntries.Clear();
}
private:
// Not to be implemented
nsCategoryCache(const nsCategoryCache<T>&);
nsCString mCategoryName;
RefPtr<nsCategoryObserver> mObserver;
nsCOMArray<T> mCachedEntries;
};
#endif